The lateral arcuate ligament is a thickening of the posterior fascia of the transversus abdominis, arching from the transverse process of L1 laterally to the twelfth rib. It forms the posterolateral origin of the diaphragm, bridging over the quadratus lumborum muscle. The subcostal nerve (T12) and iliohypogastric nerve (L1) pass posterior to the lateral arcuate ligament as they enter the posterior abdominal wall.
Forms the lateral diaphragmatic attachment arch over the quadratus lumborum; transmits diaphragmatic tension to the twelfth rib and L1 transverse process; maintains the integrity of the posterior diaphragmatic border.
The lateral arcuate ligament is relevant in retroperitoneal laparoscopic adrenalectomy and posterior laparoscopic approaches to the retroperitoneum, where its division provides access to the perirenal space and adrenal gland. In thoracoabdominal approaches to the thoracolumbar spine, the lateral arcuate ligament is divided as part of the diaphragmatic detachment. Entrapment of the subcostal nerve posterior to the lateral arcuate ligament produces a lateral abdominal wall pain syndrome exacerbated by trunk extension.
The subcostal nerve compressed as it passes posterior to the lateral arcuate ligament produces lateral flank and abdominal wall pain and paresthesiae in a horizontal distribution along the subcostal dermatome, worsened by trunk extension; injection of local anaesthetic at the posterior end of the arcuate ligament relieves the entrapment pain.
